A&P Exam 3 Flashcards
name the 5 functions of the digestive system
ingestion, digestion (mechanical- physical and chemical- enzymes), absorption, compaction, and defecation
micronutrients
can be absorbed directly from ingested food
macronutrients
broken down into monomers by hydrolysis reactions
the 3 layers of the mucosa of the GI tract wall include
epithelium, laminate propria, and muscularis mucosa
what is between the muscularis mucosae and submucosa layer?
the submucosal nerve plexus
what is included in the muscularis externa?
inner circular layer and outer longitudinal layer
what is the serosa layer made of?
areolar tissue and mesothelium
what is the epithelium of the GI tract wall made up of?
mostly simple columnar
in what areas is the GI tract wall made up of stratified squamous epithelium?
the mouth to the esophagus and lower anal canal
what is the lamina propria made up of?
loose connective tissue, MALT (lymphoid tissue that helps fight against pathogens)
what is the muscularis mucosase made up of?
smooth muscle
where do nutrients get absorbed into? lipids? lipid-soluble vitamins?
nutrients are absorbed into the blood and lipids and the vitamins are absorbed in the lymphatic capillaries
what is the submucosa made up of?
loose areolar and dense irregular CT
define mixing within the GI tract
the intestine separates into many different segments so bolus is separated and then pushed together
what does the submucosa contain apart from tissue?
blood vessels, lymphatic vessels, a nerve plexus, and mucus glands in some areas
what is derived from efferent division
somatic NS (motor neurons that activate skeletal muscles) and Autonomic NS
the autonomic NS divides into 3 sections
sympathetic NS, parasympathetic NS, and the enteric NS
what does the sympathetic NS and parasympathetic NS affect?
smooth and cardiac muscle, exocrine glands, and endocrine glands
enteric NS affects that
digestive organs only
the Enteric NS is located where
the submucosal plexus and myenteric plexus
the enteric NS coordinates what
the mixing and propulsion reflexes in the GI tract
what is between the 2 layers of the muscularis mucosae?
the myenteric plexus
the parasympathetic ___ GI tract activities
promotes
the ___ and ___ go to the myenteric plexus and stimulate the ____
vagus nerve and pelvic splanchnic nerve, smooth muscle and secretory cells respectively
the sympathetic ___ GI tract activities
opposes
the ___ and ___ go to the submucosal plexus and stimulate the ____
sympathetic ganglia and preganglionic fibers (from thoracic and lumbar spinal cord) and stimulate the postganglionic fibers and blood vessels respectively
describe the short reflex pathway (myenteric reflexes)
the stimulus stimulates chemo, mechano, and osmoreceptors to stimulate the enteric NS which either goes directly to the effector cells like smooth muscle or endocrine glands or it goes to the endocrine cells to stimulate hormone release into the blood which stimulates the effector cells and leads to a response
describe the long reflex pathway (vagovagal reflexes)
the stimulus stimulates chemo, mechano, and osmoreceptors to stimulate the central nervous system which stimulates the autonomic NS, and then the enteric NS which stimulates the effector cells or the endocrine cells that eventually stimulate said effector cells for the targeted response
what can be secreted to regulate the digestive tract?
paracrine secretions
what hormones are released to regulate the digestive tract?
gastrin and secretin
what cells is the oral cavity mostly made up of?
mostly nonkeratinized stratified squamous epithelium
how does mastication help the digestion process?
increases the surface area of the food to allow it to be exposed to digestive enzymes, promotes salivation
what parts of the oral cavity are keratinized?
the lips, portions of the tongue, small part of the hard palate
what is mastication controlled by?
the nuclei in medulla and pons, also called the mastication center
saliva is mostly made up of what?
99.5% water and a mix of solutes, salivary amylase (antibacterial), mucin (antiviral), and lysozyme
salivary amylase starts what
the chemical breakdown of starch
what are the 2 types of secretory cells within salivary glands
mucuous and serous cells
mucous cells secrete what
mucin, forming mucus upon hydration
serous cells produce what
watery fluid with electrolytes and salivary amylase
intrinsic salivary glands are where
oral cavity
extrinsic salivary glands are located where
outside oral cavity
between intrinsic and extrinsic, which produce the most saliva?
extrinsic
what are the 3 extrinsic salivary glands
parotid, submandibular, and sublingual glands
intrinsic salivary glands ____ release secretions independent of food
continuously
lingual, labial, palatine, buccal glands are located where? what is the gland type these are considered?
they’re unicellular glands, tongue, labial, roof of mouth, inside of cheek
what is the enzyme that intrinsic salivary glands release, specifically the lingual glands?
lingual lipase, which begins digestion
which of the extrinsic salivary glands hold 20-30% of saliva?
parotid salivary gland, the largest one
infection of the parotid glands causes what
mumps
which extrinsic gland produces 60-70% of saliva
submandibular salivary gland
which extrinsic salivary gland contributes to 3-5% of saliva?
sublingual salivary gland
what 3 skeletal muscle pairs form the pharynx?
superior, middle, and inferior pharyngeal constrictors
what type of epithelium is the pharynx lined with?
nonkeratinized stratified squamous
superior esophageal sphincter closes when
you inhale
inferior esophageal sphincter helps
keep stomach contents from regurgitating with the help of diaphragm muscles
the esophagus contains ____ in its submucosa, why is this important?
lots of elastic fibers to allow stretching during swallowing
an esophagus’ muscularis layer has both ____ and ____ muscle
skeletal in the superior 1/3 and smooth in the inferior 1/3, in the middle 1/3, there’s both
what are the 3 phases of deglutition
oral phase (voluntary), pharyngeal phase (involuntary), esophageal (involuntary)
describe the voluntary phase of deglutition
the food is pushed by the tongue against the hard palate and moves to the oropharynx
describe the pharyngeal phase of deglutition
as the bolus goes to through the oropharynx, the soft palate and uvula rise and cover the nasopharynx, and the larynx elevates too so the epiglottis closes over the laryngeal inlet
describe the esophageal phase of deglutition
the soft palate and uvula return to their original position, superior esophageal sphincter closes, the inferior esophageal sphincter opens and allows bolus to pass through, overall the peristalsis contractions help move the bolus to the stomach
how do the tunics of the stomach differ from the “default” tunic pattern?
there’s an extra muscularis layer– the oblique layer and has different types of cells
surface mucous cells in the stomach release what
alkaline mucin
mucous neck cells in the stomach release what
acidic mucin, alkaline mucin too but not as much as surface cells
parietal cells in the stomach release what
HCl and intrinsic factor
what are the 7 major functions of stomach acid
sterilize food, digest proteins, activate pepsin, activate intrinsic factor, stimulate bile and enzyme delivery, close the esophageal sphincter, and open the pyloric sphincter
How is HCl formed in the parietal cells?
when Cl- is released by red blood cells, the it passes through the cell. CO2 reacts with water to from H2CO3 which divides into HCO3 and H+ to which the H+/K+ pump. The Cl- and H+ react and form HCl while the HCO3 that was produced is taken up by RBCs or traveling throughout the blood
what activates intrinsic factor?
vitamin B12 or cobalamin
Chief cells in the stomach release what
pepsinogen and gastric lipase
What happens when HCl and pepsinogen react?
the peptide is removed and pepsin is produced, activated form of pepsinogen, which can be used to reactivate the reaction or react with dietary proteins, resulting in denatured proteins and then oligopeptides
what’s the main source of lipase? other sources?
lipase, then lingual gland, gastric gland, lungs, intestinal mucosa, milk, adipose tissue, and leukocytes
enteroendocrine cells in the stomach release what
serotonin and histamine (EDL cells) and somatostatin (d cells) and gastrin (G cells)
describe the process of enteroendocrine cell products
the enteric neuron releases acetylcholine which stimulates the parietal cell to release HCl, an acid, which decreases pH which stimulates D-cells who secrete somatostatin which inhibit G-cells
what does acidic mucin help with?
maintaining acidic conditions in stomach, and protecting the lining from abrasion and injury
zymogen
inactive precursor of pepsin
how does the mucous layer help the stomach lining?
it protects the lining from ulceration and from gastric enzymes with high acidity
what does gastric lipase do?
digest fats
what are the functions of HCl in the stomach?
breaks down plant cell walls and animal connective tissue, denatures proteins, converts pepsinogen into active pepsin, and kills most microorganisms entering stomach
intrinsic factor is important for what?
it’s required for absorption of vitamin B12 in ileum and needed to produce normal erythrocytes
contractions of smooth muscle in the stomach wall mix ___ with ___ to form ____
bolus, gastric secretions, chyme
peristaltic waves result in ____ that move stomach contents towards the ____
pressure gradients, pyloric region
____ in the stomach increases force in pylorus against ___
pressure gradient, pyloric sphincter
when the ___ opens, a small volume of ___ enters the duodenum and then it closes which causes ____
pyloric sphincter, chyme, retropulsion
what is the stimulus(i) of the cephalic phase? receptors?
thought, smell, sight, or taste of food and the 5 sense are the receptors
after the receptor receives the stimulus in the cephalic phase, the sensory input includes
an increase in nerve signals from the cerebral cortex and hypothalamus
what is the integration center of the cephalic phase
the medulla oblongata
what is the motor output of the cephalic phase? effector?
an increase in nerve signals that are relayed along the vagus nerve to the stomach. the effector is the stomach which increases the force of contraction and release of secretions
what is the stimulus and receptor of the gastric phase?
the presence of food in the stomach and the baroreceptors (which detect stretch in the stomach wall) and chemoreceptors (which detect the high protein or high pH in stomach content)– these are located in the plexus
what is the sensory input of the gastric phase and where is it integrated?
increases nerve signals to the medulla oblongata
what is the motor output and effector of the gastric phase?
an increase in nerve signals sent along the vagus nerve to the stomach which is stimulated to increase its force of contraction and release of secretions.
Histamine and gastrin continue the stimulation of
acid and enzyme secretion
what is the stimulus and receptor of the intestinal phase?
the presence of acidic chyme/low pH in duodenum is detected by the chemoreceptors in the wall
what is the sensory input and integration center of the intestinal phase?
a decrease in nerve signals to the medulla oblongata
what is the motor output and effector of the intestinal phase?
a decrease in nerve signals relayed along vagus nerve to stomach which decreases its force of contraction and secretions released.
what hormones are released during intestinal phase?
cholecystokinin (CCK) and secretin
the only hormone released during the gastric phase is
gastrin which increases the force of stomach contractions and release of secretions and also contracts the pyloric sphincter.
what is an inhibitory event for the cephalic phase?
loss of appetite or depression
what is an inhibitory event for the gastric phase?
very low acidity in stomach and emotional stress. the low acidity targets the g cells to decrease gastrin secretion. stress activates the sympathetic NS to override the parasympathetic controls
what is an inhibitory event for the intestinal phase?
bloating of duodenum, presence of fatty, acidic, or hypertonic chyme and/or irritants in duodenum, and partially digested food in duodenum, leading tot he enterogastric reflex and release of entergastrones
gastric bypass
a surgical treatment for obesity
gastric ulcer
erosion of a part of the stomach due to helicobacter pylori
vomiting center is stimulated by
odor, smell, taste and is on the right side of the brain
chemoreceptor trigger zone for vomiting is triggered by
drugs and toxins, on the left side of brain
gastric reflux and reflux esophagitis
inflammation of esophagus due to acidic chyme refluxing into esophagus
how long do ingested nutrients reside in the small intestine?
12 hours
the small intestine absorbs most ____ and large percentage of ____,____, and_____
nutrients, water, electrolytes, and vitamins
the duodenum is receives what
chyme and accessory gland secretions
jejunum does what
chemical digestion and nutrient absorption
ileum does what
continues the absorption of digested material
duodenum is mostly ____ while jejunum and ileum is _____
retroperitoneal (behind peritoneum) intraperitoneal
enzymes on the lumen of the small intestines digest what
mono and disaccharides
monosaccharides are absorbed into the cell by ____ diffusion or by ____ transport with Na+
facilitated, secondary active
absorbed monosaccharides leave the cell by ___ and enter the ___, the ___ distributes the nutrients throughout the body
facilitated, blood, bloodstream
circular folds are more numerous in ___ and ____ less in ____
duodenum and jejunum, ileum
the circular folds are also called what? and they increase what
place circulares, surface area
the ____ increase the surface area by 10x and contain ___ and ____
villi, blood capillaries and lacteals
____ increase the surface area by 20x and is on ____ epithelial cells
microvilli, simple columnar, they are extensions of plasma membrane
the epithelium of the intestines include
goblet cells and enterocytes (simple columnar w/microvilli)
lacteals
lymphatic capillaries within the villi that absorb lipids and lipid-soluble vitamins
what do goblet cells produce?
mucin, precursor of mucous
what do enteroendocrine cells release?
hormones like cholecystokinin CCK and secretin
what do paneth cells produce?
lysozymes and other antimicrobial agents
what does the duodenal submucosal (Brunner) gland produce?
alkaline mucus which protects the duodenum from chyme
the smooth muscle of the small intestine mixes ___ with ____ and moves it against new areas of ____
chyme, gland secretions, brush border
early intestinal phase is
segmentation, the backward and forward motion that mixes chyme with gland secretions and intestinal juice
contractions in segmentation is initiated by ___ and spread through muscularis via ____
pacemaker cells, gap junctions
late intestinal phase is
peristalsis which repeats until all content is moved to large intestine
peristalsis is initiated by ____ which is released from the duodenum
motilin
migrating motility complex
successive waves of contractions
describe the gastroileal reflex
ileum contracts and the ileocecal sphincter relaxes (CCK causes this), the cecum relaxes and moves contents from ileum to cecum in response to food in stomach, the ileocecal valve contracts to prevent back flow
gallbladder
stores, concentrates, and releases bile
liver
produces bile
bile contains
minerals, cholesterol, neutral fats, phospholipids, bile pigments (bilirubin), and bile salts (lecithin and bile acids)
what do bile salts do to fat globules?
they coat the broken up droplets– emulsification
how do gallstones form?
bile becomes excessively concentrated with wastes
hepatocytes can
process blood-born nutrients (arrive from gut through the hepatic portal vein), store fat-soluble vitamins, detoxification, recycle erythrocytes, and produce bile
cirrhosis
hepatocytes are replaced by fibrous scar tissue
what are the effects of cirrhosis
they compress blood vessels and bile ducts in the liver
hepatic portal hypertension
compression of blood vessels in the liver
what causes cirrhosis
chronic alcoholism, liver disease, drugs, or toxins, and viral infections like hepatitis B or C
what are the symptoms of cirrhosis
fatigue, weight loss, nausea, pain in the upper right quadrant, and more severe cases have jaundice, edema, ascites, itching, toxin accumulation, dilated veins of esophagus
what causes gallstones?
condensations of cholesterol or calcium and bile salts
what are symptoms of gallstones
severe pain, nausea, vomiting, indigestion, bloating, symptoms are worse after a fatty meal
what is pancreatic juice made up of?
sodium bicarbonate and enzymes like zymogen proteases and activated amylase, lipase, and nuclease
what kinds of zymogen proteases are involved in pancreatic juice
trypsinogen,, chymptrypsinogen, procarboxypeptidase
the enzymes in the pancreas need ___ for optimal activity
bile
what does sodium bicarbonate add to the digestion system?
neutralize the acidic gastric juice entering the small intestine, adjusts pH to allow the proper function of digestive enzymes
how do pancreatic enzymes affect the digestion process
amylase digests sugars, trupsina nd chymotrypsin digest proteins, lipase digests fats, nuclease digest RNA and DNA back into their nucleic acid building blocks
what’s a hormone released in response to fatty chyme
cholecystokinin CCK
what is the role of CCK?
stimulates gallbladder to strongly contract and release bile, pancreas to release pancreatic juice, relax the smooth muscle within the hepatopancreatic ampulla to allow the entry of bile and pancreatic juice into the small intestine, and stops stomach motility and release of gastric secretions (overall stomach movement)
what is released in released in response to increased chyme acidity
secretin
CCK and secretin are released from
the small intestine
how does secretin affect digestion?
stimulates the release of alkaline solution with bicarbonate from liver and pancreas, neutralizes acidic chyme, and inhibits gastric secretions and stomach motility
what are the functions of the large intestine?
absorbs water and electrolytes from remaining digested material, watery chyme compacted into feces, stores feces until eliminated through defecation
muscularis externa is unusual where
colon
the large intestine does not have intestinal ___, but has numerous ____ extending towards the ____ which help to ______
villi, intestinal glands, muscularis mucosa, lubricate undigested material
the cecum and colon have 2 layers of smooth muscle in their muscularis
outer longitudinal layer and the discontinuous layer which forms the teniae coli
how much water per day is secreted into the lumen of GI tract?
6L which includes saliva, gastric juice, and mucus
what is the role of bacterial flora in the large intestine?
synthesize vitamins B and K, ferment indigestible carbohydrates like fiber–cellulose, and release irritating acids and gases which aid in propulsion
describe the neural pathway that stimulates defecation
poop stimulates baroreceptors in rectal wall due to stretching, which sends nerve signals from sensory neurons through the spinal cord, which go through cerebral cortex and relays nerve signals along the motor neurons which contract the smooth muscle of the sigmoid colon and rectum, output to the internal anal sphincter decreases, relaxing it. the decision to defecate is controlled by cerebral cortex, using the valsalva maneuver to eliminate the feces
haustral churning
relaxed haustrum fills with material, distention stimulates reflex contractions in muscularis, increasing churning and moves materials to more distal haustra
mass movements in large intestine
powerful contractions involve the teniae coli which propel the fecal material towards the rectum, 2-3x a day
gastrocolic reflex
started by stomach distention which causes a mass movement
when is voluntary defecation learned by? what does it entail?
age 3, relaxation of external (voluntary) anal sphincter
inflammation bowel disease (IBD) includes
Cohn disease and ulcerative colitis
irritable bowel syndrome (IBS)
affects 1 in 5 Americans, abnormal function of colon, more common in women, involves cramps, bloating, constipation, diarrhea, treated with diet, medication, stress reduction
Crohn’s disease
autoimmune disorder, happens in young adults, intermittent and relapsing episodes of cramping and diarrhea
ulcerative colitis
similar to Crohn’s but only involves the large intestine
